1. Field of the Invention
The present invention relates to mobile user equipment, and particularly, to an International Mobile Equipment Identification (IMEI) coding method for a Global System for Mobile Communications (GSM) user equipment (UE).
2. Description of the Related Art
In general, a GSM user equipment (UE), also known as a mobile, subscriber unit, remote station or mobile terminal, supports an international roaming service using a Subscriber Identity Module (SIM) card. The SIM card is a type of smart card that provides a user with the ability to perform mobile communication operations. A SIM card may be removed from one UE and installed into another UE.
In order to provide an international roaming service, the UE has an International Mobile Subscriber Identity (IMSI) and an International Mobile Equipment Identity (IMEI) for securing personal mobility. The IMSI is stored on the SIM card while the IMEI, which is an equipment identity of the UE, is stored in a flash memory internal to the UE.
FIG. 1 is a flow chart illustrating a method of storing an IMEI of the UE in accordance with the related art. The IMEI can be easily written by a simple attention command (AT command) through an IMEI utility, such as an IMEI writing program running on a personal computer (PC).
Referring to FIG. 1, the UE manufacturer inputs an AT command containing an IMEI to the UE by using an IMEI writing program of a PC (S110). When the AT command is inputted to the UE, a Mobile Station Modem (MSM) of the UE checks whether the AT command which has been inputted from the IMEI writing program is an IMEI write command (S120). If the inputted command is the IMEI write command, the IMEI contained in the AT command is stored in a flash memory of the UE (S130).
As described above, the UE supporting an international roaming service stores the IMEI for securing the personal mobility in the flash memory. Thus, mobile communications providers can trace a UE that has been reported as lost or stolen, using the IMEI recorded in its flash memory.
However, a drawback to the above coding function is that the IMEI can be easily overwritten. Thus, a third person may easily use the lost or stolen UE after rewriting the IMEI. Also, it would be difficult for a mobile communications provider to trace the lost or stolen UE after the IMEI is rewritten.
Accordingly, to prevent a third person from illegally using the lost or stolen UE by writing a new IMEI, UE manufacturers are using an IMEI coding method by hardware. However, although effectively preventing unauthorized use of a lost or stolen UE by a third person, the IMEI coding method by hardware makes it difficult for a new IMEI to be designated upon an authorized user's request. Currently, in order to designate a new IMEI by hardware, the entire UE, or a circuit board within the UE, must be replaced by a UE manufacturer or service center.